Hi,

When, like in pg 15 of TOPswitch jx datasheet, the NPN is used...do you just consider it as an opto with  a greater CTR value?...ie for the error amplifier/modulator transfer function.

(as in Basso's book chapter about TOPswitch).

Also, please may i ask which is the App note on feedback loop for TOPswitch? (we use TOP256GN).

Also, in pg 15 of TOPswitch jx datasheet, why is R19 used?...Basso doesnt use this in his book chapter about TOPswitch (not for type 1 , 2 or 3)....what is the transfer function when R19 is used?

Also, why is it that neither PI Expert or PI designer use the NPN in a Darligton pair with the feedback opto in order to reduce the optocoupler current?

Also, please may i ask, why is it that the attached AN-57 no longer appears on Power.com website?